Re: [Groff] Question about .substring

[Ralph Corderoy]

Hi Tadziu,

> > second parameter that gives an empty string, unlike the
> > [startindex, endindex) interval where endindex is exclusive,
> > e.g. Python.
> 
> But that's not to say that the python way is in any way
> more intuitive or useful.  Example:
> 
>     >>> print [1,2,3,4,5,6,7,8][-1] 
> --> 8
>     >>> print [1,2,3,4,5,6,7,8][-2:-1] 
> --> [7]
> 
> which makes negative indices pretty useless for retrieving
> a subrange that includes the last element...

If the colon is given then either or both of the indices can be omitted.

    >>> s = 'abcdefghij'
    >>> s[3], s[:3], s[3:], s[-3:], s[:]
    ('d', 'abc', 'defghij', 'hij', 'abcdefghij')

The other nice thing about [) is that you can shuffle the indexes along
and cover the whole array, i.e. the end index last time becomes the
start index this time.

    >>> s = 'abcdefghij'
    >>> s[0:3], s[3:6], s[6:9], s[9:12]
    ('abc', 'def', 'ghi', 'j')

[) has become the norm in "new" languages?
https://en.wikipedia.org/wiki/Interval_%28mathematics%29#Notations_for_intervals

Cheers, Ralph.